Corrugated fiberboards are, for instance, typical of a conventional member fabricated from paper sheets having hollow portions parallel to one another.
The corrugated fiberboards are classified into A to E-flute corrugated fiberboards according to the size of flutes, and also classified into a single faced corrugated fiberboard, a double faced corrugated fiberboard, a double wall corrugated fiberboard and a triple wall corrugated fiberboard according to differences in structure.
These corrugated fiberboards are used for forming packaging boxes, cushioning materials and other packaging members. Recently, a proposal has been made that a layered corrugated fiberboard be used for forming cushioning materials for packaging, frame structures for packaging, and core materials of heat-insulating panels or the like.
The corrugated fiberboard and the layered corrugated fiberboard member as described above have the following problems.
Namely, one of the problems is that the corrugated fiberboard must be fabricated by the use of base boards, and as a result, it is not possible to freely select a material (i.e., base board) for the corrugated fiberboard.
Another problem is that since the corrugated fiberboard is a standardized product, there are restrictions on selection of void content (which means a ratio of the sectional area of hollow portions to the whole sectional area in a section crossing at a right angle to the hollow portions) for the corrugated fiberboard.
A further problem is that it is not possible to freely select a sectional shape for the hollow portions.
In connection with the above problems, a still further problem is that cushioning materials, packaging frame structures and other packaging members which are formed by the use of layered corrugated fiberboards are limited in selection of their hardness or the strength of elasticity from the viewpoint of design. Coincidentally, this problem means that their use is restricted within narrow limits.
A yet further problem is that several pieces of base boards and linerboard, and besides, a large number of steps, are required for fabricating a corrugated fiberboard, and as a result, high fabrication cost is inevitable.